Fixing onConflict case with existing column used

[deusaquilus]

In on-conflict queries where the "existing" column is used in multiple clauses and aliased with different names the 2nd etc... aliases are invalid because they don't even exist. For the excluded references, the EXCLUDED term should be used but for the "existing" column nothing should be used at all.

 ins.onConflictUpdate(_.i, _.s)(
    (t, e) => t.l -> foo(t.l, e.l), (tt, ee) => tt.l -> bar(tt.l, ee.l)
  )

// (Scroll right ->)
//                                                                                                                            This doesn't exist!!
//                                                                                                                                    v
// > INSERT INTO TestEntity AS t (s,i,l,o,b) VALUES (?, ?, ?, ?, ?) ON CONFLICT (i,s) DO UPDATE SET l = foo(t.l, EXCLUDED.l), l = bar(tt.l, EXCLUDED.l)

Instead we should completely drop the table name and just use the column:

INSERT INTO TestEntity AS t (s,i,l,o,b) VALUES (?, ?, ?, ?, ?) 
ON CONFLICT (i,s) 
DO UPDATE SET l = foo(/*-- drop: t. --*/ l, EXCLUDED.l), l = bar(/*-- drop: tt. --*/ l, EXCLUDED.l)